The SSI payment for someone earning $400 per month is calculated as follows.
400 - 85 (earned income deduction 65 and general exclusion 20) = 315/2 = 157.50
157.50 = Countable income
To determine new SSI amount:
623.00 = Federal Benefit Rate
623.00-157.50 = 465.50
$465.50 = New SSI check
New total monthly income= 465.50 + 400 (earnings) + 362(Adult Public Assistance) = $1227.50